As is well known, ordinary coffee is made from the seeds of the fruits of a plant belonging to the genus Coffea by a series of operations.
These operations start with removing the seeds from the fruit and include seed washing, drying and decorticating operations.
The typically green-colored coffee seeds are then roasted, i.e. applied heat at a set temperature, for a length of time selected to give coffee the desired flavor and taste.
Thereafter, the roasted seeds are cooled, ground to a desired grain size and packaged, usually under a vacuum to best preserve their flavor.
Also recognized is that, of all the above coffee seed processing operations, the roasting process is of vital importance to the quality of the end product.
The roasting process has been carried out traditionally in continuous, or discontinuous, drum apparatus in which a chosen blend of green coffee seeds, usually from different crops, is heated to a temperature of 200° to 220° C. by means of a stream of hot air and kept at such a temperature for a time that varies between 12 and 20 minutes, depending on the flavor and taste to be given to the end product.
A drawback of traditional roasting is that the coffee seed has to be applied a relatively high temperature through a sufficient time span for the roasting effect to reach the core region of the seed and so yield a coffee product of proper quality.
Under the above conditions, the outer portions of the seeds, or whole seeds of a smaller size, are roasted to excess, which affects the quality of the end product because of alteration or decomposition of many substances therein contained.
More particular, in the traditional roasting process, sugary substances in the seeds tend to caramelize, fats tend to oxidise, cellulose tends to char enough to lose its capacity for trapping flavor, and small amounts of decomposition products are formed such as hydroquinone, methylamine, pyrrole, and acetone.
Another drawback of traditional roasting is that a large proportion of the volatile substances responsible for the coffee flavor, and either contained originally in the seeds or generated by the roasting process, is lost together with the fumes escaping through the chimney. Caffeine too goes wasted in substantial proportions (up to 20% of its original amount), either by sublimation or decomposition. It has been found that caffeine has, itself, anti-mutagenous activity, in the sense that it can inhibit the mutagenous effects of a number of chemicals. Caffeine is reportedly effective to restore the mitosis and phosphorylation cycle back to normal in irradiated cells.
But when caffeine decomposes, it may release aliphatic di-carbonyl compounds that are highly reactive, as well as being mutagenous for mammalian cells.
Lastly, traditional coffee seed roasting is never applied evenly to the seeds being processed, because the process depends heavily on such physical parameters of the seeds as their size, density, and moisture content, which may vary considerably.
The underlying technical problem of this invention is to provide a process for producing roasted coffee or a surrogate thereof, which can overcome the aforementioned drawbacks of the prior art. In other words, a process in which roasting can be applied uniformly and without the seeds becoming over-roasted, so as to yield a quality product.